Spatial heterogeneity in size-structure of meiofaunal-sized invertebrates on small-spatial scales (Meters) and its implications

1984 ◽  
Vol 78 (3) ◽  
pp. 221-235 ◽  
Author(s):  
John C. Kern ◽  
Susan S. Bell
Keyword(s):  
Spatial Heterogeneity ◽  
Size Structure ◽  
Spatial Scales

scholarly journals Spatial scale-dependent land–atmospheric methane exchanges in the northern high latitudes from 1993 to 2004

2014 ◽  
Vol 11 (7) ◽  
pp. 1693-1704 ◽  
Author(s):  
X. Zhu ◽  
Q. Zhuang ◽  
X. Lu ◽  
L. Song
Keyword(s):  
Spatial Heterogeneity ◽  
Spatial Scale ◽  
Water Table ◽  
Spatial Scales ◽  
Grid Cell ◽  
High Latitudes ◽  
Atmospheric Methane ◽  
Ch4 Emissions ◽  
Biogeochemical Models ◽  
Macro Scale

Abstract. Effects of various spatial scales of water table dynamics on land–atmospheric methane (CH4) exchanges have not yet been assessed for large regions. Here we used a coupled hydrology–biogeochemistry model to quantify daily CH4 exchanges over the pan-Arctic from 1993 to 2004 at two spatial scales of 100 km and 5 km. The effects of sub-grid spatial variability of the water table depth (WTD) on CH4 emissions were examined with a TOPMODEL-based parameterization scheme for the northern high latitudes. We found that both WTD and CH4 emissions are better simulated at a 5 km spatial resolution. By considering the spatial heterogeneity of WTD, net regional CH4 emissions at a 5 km resolution are 38.1–55.4 Tg CH4 yr−1 from 1993 to 2004, which are on average 42% larger than those simulated at a 100 km resolution using a grid-cell-mean WTD scheme. The difference in annual CH4 emissions is attributed to the increased emitting area and enhanced flux density with finer resolution for WTD. Further, the inclusion of sub-grid WTD spatial heterogeneity also influences the inter-annual variability of CH4 emissions. Soil temperature plays an important role in the 100 km estimates, while the 5 km estimates are mainly influenced by WTD. This study suggests that previous macro-scale biogeochemical models using a grid-cell-mean WTD scheme might have underestimated the regional CH4 emissions. The spatial scale-dependent effects of WTD should be considered in future quantification of regional CH4 emissions.

scholarly journals A new uncertainty estimation approach with multiple datasets and implementation for various precipitation products

2020 ◽  
Vol 24 (4) ◽  
pp. 2061-2081 ◽  
Author(s):  
Xudong Zhou ◽  
Jan Polcher ◽  
Tao Yang ◽  
Ching-Sheng Huang
Keyword(s):  
Spatial Heterogeneity ◽  
Spatial Scales ◽  
Three Dimensional ◽  
Variance Partitioning ◽  
Uncertainty Estimation ◽  
The Other ◽  
New Approach ◽  
Multiple Datasets ◽  
Uncertainty Estimates ◽  
Spatiotemporal Scales

Abstract. Ensemble estimates based on multiple datasets are frequently applied once many datasets are available for the same climatic variable. An uncertainty estimate based on the difference between the ensemble datasets is always provided along with the ensemble mean estimate to show to what extent the ensemble members are consistent with each other. However, one fundamental flaw of classic uncertainty estimates is that only the uncertainty in one dimension (either the temporal variability or the spatial heterogeneity) can be considered, whereas the variation along the other dimension is dismissed due to limitations in algorithms for classic uncertainty estimates, resulting in an incomplete assessment of the uncertainties. This study introduces a three-dimensional variance partitioning approach and proposes a new uncertainty estimation (Ue) that includes the data uncertainties in both spatiotemporal scales. The new approach avoids pre-averaging in either of the spatiotemporal dimensions and, as a result, the Ue estimate is around 20 % higher than the classic uncertainty metrics. The deviation of Ue from the classic metrics is apparent for regions with strong spatial heterogeneity and where the variations significantly differ in temporal and spatial scales. This shows that classic metrics underestimate the uncertainty through averaging, which means a loss of information in the variations across spatiotemporal scales. Decomposing the formula for Ue shows that Ue has integrated four different variations across the ensemble dataset members, while only two of the components are represented in the classic uncertainty estimates. This analysis of the decomposition explains the correlation as well as the differences between the newly proposed Ue and the two classic uncertainty metrics. The new approach is implemented and analysed with multiple precipitation products of different types (e.g. gauge-based products, merged products and GCMs) which contain different sources of uncertainties with different magnitudes. Ue of the gauge-based precipitation products is the smallest, while Ue of the other products is generally larger because other uncertainty sources are included and the constraints of the observations are not as strong as in gauge-based products. This new three-dimensional approach is flexible in its structure and particularly suitable for a comprehensive assessment of multiple datasets over large regions within any given period.

Landscape Heterogeneity and Dynamics

2019 ◽  
pp. 42-126
Author(s):  
Kimberly A. With
Keyword(s):  
Landscape Ecology ◽  
Spatial Heterogeneity ◽  
Landscape Structure ◽  
Landscape Heterogeneity ◽  
Spatial Scales ◽  
Anthropogenic Disturbances ◽  
Ecological Processes ◽  
Disturbance Dynamics ◽  
Wide Range ◽  
Over Time

Heterogeneity is a defining characteristic of landscapes and therefore central to the study of landscape ecology. Landscape ecology investigates what factors give rise to heterogeneity, how that heterogeneity is maintained or altered by natural and anthropogenic disturbances, and how heterogeneity ultimately influences ecological processes and flows across the landscape. Because heterogeneity is expressed across a wide range of spatial scales, the landscape perspective can be applied to address these sorts of questions at any level of ecological organization, and in aquatic and marine systems as well as terrestrial ones. Disturbances—both natural and anthropogenic—are a ubiquitous feature of any landscape, contributing to its structure and dynamics. Although the focus in landscape ecology is typically on spatial heterogeneity, disturbance dynamics produce changes in landscape structure over time as well as in space. Heterogeneity and disturbance dynamics are thus inextricably linked and are therefore covered together in this chapter.

scholarly journals Long-term shifts in the colony size structure of coral populations along the Great Barrier Reef

2020 ◽  
Vol 287 (1936) ◽  
pp. 20201432
Author(s):  
Andreas Dietzel ◽  
Michael Bode ◽  
Sean R. Connolly ◽  
Terry P. Hughes
Keyword(s):  
Great Barrier Reef ◽  
Colony Size ◽  
Size Structure ◽  
Coral Cover ◽  
Spatial Scales ◽  
Reproductive Capacity ◽  
Barrier Reef ◽  
Size Frequency Distribution ◽  
Coral Colony ◽  
Recovery Potential

The age or size structure of a population has a marked influence on its demography and reproductive capacity. While declines in coral cover are well documented, concomitant shifts in the size-frequency distribution of coral colonies are rarely measured at large spatial scales. Here, we document major shifts in the colony size structure of coral populations along the 2300 km length of the Great Barrier Reef relative to historical baselines (1995/1996). Coral colony abundances on reef crests and slopes have declined sharply across all colony size classes and in all coral taxa compared to historical baselines. Declines were particularly pronounced in the northern and central regions of the Great Barrier Reef, following mass coral bleaching in 2016 and 2017. The relative abundances of large colonies remained relatively stable, but this apparent stability masks steep declines in absolute abundance. The potential for recovery of older fecund corals is uncertain given the increasing frequency and intensity of disturbance events. The systematic decline in smaller colonies across regions, habitats and taxa, suggests that a decline in recruitment has further eroded the recovery potential and resilience of coral populations.

scholarly journals Human-induced reductions in fish predator boldness decrease their predation rates in kelp forests

2019 ◽  
Vol 286 (1900) ◽  
pp. 20182745 ◽  
Author(s):  
O. Kennedy Rhoades ◽  
Steve I. Lonhart ◽  
John J. Stachowicz
Keyword(s):  
Protected Areas ◽  
Size Structure ◽  
Spatial Scales ◽  
Ecological Impacts ◽  
Predatory Fish ◽  
Kelp Forests ◽  
Fish Predator ◽  
Spatial And Temporal Scales ◽  
Predatory Fishes ◽  
Predation Rates

Humans have restructured food webs and ecosystems by depleting biomass, reducing size structure and altering traits of consumers. However, few studies have examined the ecological impacts of human-induced trait changes across large spatial and temporal scales and species assemblages. We compared behavioural traits and predation rates by predatory fishes on standard squid prey in protected areas of different protection levels and ages, and found that predation rates were 6.5 times greater at old, no-take (greater than 40 years) relative to new, predominantly partial-take areas (approx. 8 years), even accounting for differences in predatory fish abundance, body size and composition across sites. Individual fishes in old protected areas consumed prey at nearly twice the rate of fishes of the same species and size at new protected areas. Predatory fish exhibited on average 50% longer flight initiation distance and lower willingness to forage at new protected areas, which partially explains lower foraging rates at new relative to old protected areas. Our experiments demonstrate that humans can effect changes in functionally important behavioural traits of predator guilds at large (30 km) spatial scales within managed areas, which require protection for multiple generations of predators to recover bold phenotypes and predation rates, even as abundance rebounds.

Small-scale patterns of distribution and size-structure of the intertidal littorinid Littorina unifasciata (Gastropoda: Littorinidae) in New South Wales

1994 ◽  
Vol 45 (4) ◽  
pp. 635 ◽  
Author(s):  
MG Chapman
Keyword(s):  
Size Structure ◽  
New South ◽  
Spatial Scales ◽  
New South Wales ◽  
Small Scale ◽  
Rock Surface ◽  
Strongly Correlated ◽  
Patterns Of Distribution ◽  
South Wales ◽  
Potential Factors

Within-shore and among-shore patterns of distribution, abundance and size structure of Littorina unifasciata Gray were identified on a number of shores in New South Wales. There was significant patchiness in distribution, abundance and size of L. unifasciata among patches of shore only a few metres apart, at different heights on the shore and from shore to shore. On a particular shore, the sizes of snails were strongly correlated with densities. In contrast, differences in densities at different heights from one shore to another were not correlated with mean size of snails. Density and size were each strongly correlated with the height on the shore at which snails were found. At any one height, differences in densities and size were also correlated with the distribution of particular microhabitat variables, such as the slope of the rock surface, the presence of pits and shallow pools and the presence of barnacles. Densities were also negatively correlated with densities of the large microalgae-grazing limpet Cellana tramoserica but were independent of other littorinids. A number of alternative models have been proposed to account for these patterns of distribution, abundance and size. Although processes that might account for these patterns were not investigated here, quantification of such patterns at a number of spatial scales is necessary before potential factors that might affect small-scale spatial variation in densities and sizes of L. unifasciata can be identified and investigated.

scholarly journals Spectral Heterogeneity Predicts Local-Scale Gamma and Beta Diversity of Mesic Grasslands

2019 ◽  
Vol 11 (4) ◽  
pp. 458 ◽  
Author(s):  
H. Polley ◽  
Chenghai Yang ◽  
Brian Wilsey ◽  
Philip Fay
Keyword(s):  
Optical Properties ◽  
Species Diversity ◽  
Spatial Heterogeneity ◽  
Plant Species ◽  
Near Infrared ◽  
Spatial Scales ◽  
Ground Level ◽  
Silty Clay ◽  
Least Squares Regression ◽  
Β Diversity

Plant species diversity is an important metric of ecosystem functioning, but field assessments of diversity are constrained in number and spatial extent by labor and other expenses. We tested the utility of using spatial heterogeneity in the remotely-sensed reflectance spectrum of grassland canopies to model both spatial turnover in species composition and abundances (β diversity) and species diversity at aggregate spatial scales (γ diversity). Shannon indices of γ and β diversity were calculated from field measurements of the number and relative abundances of plant species at each of two spatial grains (0.45 m2 and 35.2 m2) in mesic grasslands in central Texas, USA. Spectral signatures of reflected radiation at each grain were measured from ground-level or an unmanned aerial vehicle (UAV). Partial least squares regression (PLSR) models explained 59–85% of variance in γ diversity and 68–79% of variance in β diversity using spatial heterogeneity in canopy optical properties. Variation in both γ and β diversity were associated most strongly with heterogeneity in reflectance in blue (350–370 nm), red (660–770 nm), and near infrared (810–1050 nm) wavebands. Modeled diversity was more sensitive by a factor of three to a given level of spectral heterogeneity when derived from data collected at the small than larger spatial grain. As estimated from calibrated PLSR models, β diversity was greater, but γ diversity was smaller for restored grassland on a lowland clay than upland silty clay soil. Both γ and β diversity of grassland can be modeled by using spatial heterogeneity in vegetation optical properties provided that the grain of reflectance measurements is conserved.

scholarly journals A hydrological emulator for global applications – HE v1.0.0

2018 ◽  
Vol 11 (3) ◽  
pp. 1077-1092 ◽  
Author(s):  
Yaling Liu ◽  
Mohamad Hejazi ◽  
Hongyi Li ◽  
Xuesong Zhang ◽  
Guoyong Leng
Keyword(s):  
Spatial Heterogeneity ◽  
Computational Efficiency ◽  
Spatial Scales ◽  
Computational Cost ◽  
Infiltration Capacity ◽  
Vic Model ◽  
Total Runoff ◽  
Computation Efficiency ◽  
Annual Total ◽  
Distributed Scheme

Abstract. While global hydrological models (GHMs) are very useful in exploring water resources and interactions between the Earth and human systems, their use often requires numerous model inputs, complex model calibration, and high computation costs. To overcome these challenges, we construct an efficient open-source and ready-to-use hydrological emulator (HE) that can mimic complex GHMs at a range of spatial scales (e.g., basin, region, globe). More specifically, we construct both a lumped and a distributed scheme of the HE based on the monthly abcd model to explore the tradeoff between computational cost and model fidelity. Model predictability and computational efficiency are evaluated in simulating global runoff from 1971 to 2010 with both the lumped and distributed schemes. The results are compared against the runoff product from the widely used Variable Infiltration Capacity (VIC) model. Our evaluation indicates that the lumped and distributed schemes present comparable results regarding annual total quantity, spatial pattern, and temporal variation of the major water fluxes (e.g., total runoff, evapotranspiration) across the global 235 basins (e.g., correlation coefficient r between the annual total runoff from either of these two schemes and the VIC is  > 0.96), except for several cold (e.g., Arctic, interior Tibet), dry (e.g., North Africa) and mountainous (e.g., Argentina) regions. Compared against the monthly total runoff product from the VIC (aggregated from daily runoff), the global mean Kling–Gupta efficiencies are 0.75 and 0.79 for the lumped and distributed schemes, respectively, with the distributed scheme better capturing spatial heterogeneity. Notably, the computation efficiency of the lumped scheme is 2 orders of magnitude higher than the distributed one and 7 orders more efficient than the VIC model. A case study of uncertainty analysis for the world's 16 basins with top annual streamflow is conducted using 100 000 model simulations, and it demonstrates the lumped scheme's extraordinary advantage in computational efficiency. Our results suggest that the revised lumped abcd model can serve as an efficient and reasonable HE for complex GHMs and is suitable for broad practical use, and the distributed scheme is also an efficient alternative if spatial heterogeneity is of more interest.

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